Publishing is the process of production and dissemination of literature or information - the activity of making information available for public view. ...en.wikipedia.org/wiki/Publishing

When publishing is seen as a business, as a writer you hand over your text and wait for it to be published in order to get to an audience. When publishing is a process, printing is one option among others to get information to a public. For the viability of a publishing industry it is important to separate the business from the printing.

When something is to be published, many skills are needed to prepare for publication. The material may need editing, proof reading, peer review, presentation, marketing before it is readied for consumption. The skills involved maximise impact and distribution. Choosing a medium for a publication is one of them.

When publishing is not the printing business, maximising a paying public is what an author looks for. Each medium has its own cost structure and each medium has its own public. Getting this mix right and optimising for a return on investment makes the publishing business a business with a future.
Thanks,
GerardM